The three weeks of fighting between Israel and Hamas will have its longest ceasefire yet beginning at 8 AM local time on Friday, according to a statement from the U.S. Department of State.

UN Secretary General Ban Ki Moon and Secretary of State John Kerry jointly announced the ceasefire, which will last for 72 hours. It provides a critical window during which a longer truce can be negotiated, and the statement from the State Department notes that "Israeli and Palestinian delegations will immediately be going to Cairo for negotiations with the Government of Egypt, at the invitation of Egypt, aimed at reaching a durable ceasefire."

The fact both sides agreed to such a relatively lengthy halt in hostilities might offer some indication of where the operational aspects of the war are heading. Israel has destroyed "most of 32" cross-border tunnels since the operation began according to CBS News, while Hamas may see no further advantage to fighting in the face of an intensifying Israeli offensive.

Interestingly, Israeli officials have implied their military will continue its tunnel demolition efforts even with a ceasefire in place. If this turns out to be the case, then Hamas has agreed to a halt in fighting even as Israel continues in pursuing what several leaders have said is the country's prime military objective.

The ceasefire also may indicate that Israel is becoming increasingly sensitive to international criticism as the operation drags into its fourth week, especially after incidents like the apparent Israeli shelling of a UN school yesterday that killed 15 people — and drew a rare condemnation from the United States. A humanitarian ceasefire might earn the sides some goodwill at a time when international patience is waning.